The Pack is divided into Dens, one for each grade:
Kindergarten - Lions (NEW!)
1st Grade - Tigers
2nd Grade - Wolves
3rd Grade - Bears
4th Grade - Webelos
5th Grade - Arrow of Light Scouts (or Webelos II)

Each Den's activities are geared toward that age level so that the boys may achieve that particular rank. Activities get more complex and difficult at each higher rank. The Lions program operates mostly separate from the Pack, and acts as a precursor to the larger Cub Scout world. Webelos and Arrow of Light function as a transition from the adult-led model of Cub Scouts to the boy-led model of Boy Scouts. 

For more information about each rank, please click on it.